Topic 14 · Acids and bases — the scripts
What you are deciding: go-ahead for video generation on this topic, card by card.
Out of scope: articles and PP100 items (not on this page).
Here: the intro video, 6 lesson videos (4 marked by the author as “could do without a video”) and the summary video, in teaching order. Each card: the script, the attached question, then the quiz the student meets after the video.
How: tap one button per card. Taps and notes save as you go and are sent; the Notes tab shows what has gone and re-sends.
Introduction: Acids and bases
Script
| Say | Screen |
|---|---|
| Here is a lemon, a bottle of vinegar and a glass of soda water, and all three taste sour. | [the three, side by side] |
| A strip of paper dipped into each one changes color. | [a strip dips; its end changes shade] |
| Beside them is soapy water: it feels slippery, not sour. | [soapy water beside the three; a hand rubs fingers] |
| A meter gives each of these liquids a number. | [a meter readout ticking through numbers] |
| And when someone's stomach burns, one tablet stops the burning. | [a cartoon stomach; a tablet drops in] |
| So what are these two families of liquids, and what happens when they meet? | [two beakers facing each other; question mark] |
| To find out, we will look at the two families, how to tell them apart, and what they make when they react. | [the bench of liquids stays] |
| Okay, so are you ready to find out why a tablet can stop a burning stomach? | [the three replies appear] |
The ready line's poll — the attached item (no key; the intro teaches nothing)
Okay, so are you ready to find out why a tablet can stop a burning stomach?
- A Yes, let's go! — Great. Here we go.
- B Not sure yet — That's fine. We take it one step at a time.
- C Let me watch that again — Good idea. Watch it again, then come back.
Answer
No key. A poll: every reply is accepted with its friendly line.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Acids: the sour family
MAT-077 · Acid — Identify a substance as an acid from its observable properties or indicator results.
Script
| Say | Screen |
|---|---|
| Lemon juice, vinegar and soda water all taste sour. | [three beakers: lemon juice, vinegar, soda water] |
| A strip of blue paper dipped into each one turns red. | [a hatched strip dips into each; the dipped end turns dark gray; legend: hatched = blue litmus paper, dark gray = red] |
| Three liquids give one color change, so something about them is the same. | [the three beakers; the three red ends] |
| The strip is paper soaked in a dye that can change color, and it is called litmus paper. | [one strip, close up; chip: LITMUS PAPER] |
| In vinegar, the dipped end turns red. | [vinegar beaker; the strip's dipped end turns dark gray] |
| In lemon juice, the dipped end turns red. | [lemon juice beaker; same change] |
| In pure water, the paper stays blue. | [pure water beaker; the strip stays hatched] |
| In soda water, the dipped end turns red. | [soda water beaker; turns dark gray] |
| In soapy water, the paper stays blue. | [soapy water beaker; stays hatched] |
| The three sour liquids turned blue litmus paper red; the other two left it blue. | [five beakers in a row; question: Does blue litmus turn red? ticks under three, crosses under two] |
| A substance that tastes sour and turns blue litmus paper red is called an acid. | [chip: ACID over the three ticked beakers] |
| The paper changed color to show each liquid's family. A substance that does this is called an indicator. | [chip: INDICATOR over a strip] |
| Vinegar and lemon juice are acids in food. The sulfuric acid in a car battery burns skin. | [a car battery with a warning label] |
| So in a lab the test for an acid is litmus paper: never taste, never touch. | [a strip; a crossed-out tongue and a crossed-out finger] |
| So, here's what we've seen. Acids taste sour. | [the rule slide: the three ticked beakers; chip ACID; nothing else printed] |
| And acids turn blue litmus paper red. | [the three red strip ends] |
| Okay, now your turn. | [closing screen: bullets — • Acids taste sour • Acids turn blue litmus paper red] |
“Okay, now your turn.” — the attached question
Blue litmus paper is dipped into vinegar. What does the dipped end do?
- A it turns red
- B it stays blue
- C it turns green
Answer
Key: A — it turns red
Acids turn blue litmus paper red.
So the dipped end turns red.
Feedback per option
- A Vinegar is an acid, and acids turn blue litmus paper red.
- B The paper stays blue in pure water and soapy water; in vinegar the dipped end turns red.
- C Litmus paper turns red or blue, never green; in vinegar it turns red.
Quiz after the video — the mastery check, 12 items
Which of these is a physical property of vinegar?
- A It tastes sour.
- B It was bought on a Tuesday.
- C It belongs to the cook.
Answer
Key: A — It tastes sour.
You can taste vinegar and observe that it is sour.
So its sour taste is a physical property.
Feedback per option
- A A physical property is something you can observe or measure about a material, and its sour taste is one.
- B The day it was bought is not something you can observe or measure about the vinegar.
- C Who owns the bottle is not something you can observe or measure about the vinegar.
Blue litmus paper dipped in sugar water stays blue. Is sugar water an acid?
- A yes
- B no
Answer
Key: B — no
In sugar water the paper stayed blue.
So sugar water is not an acid.
Feedback per option
- A An acid turns blue litmus paper red; this paper stayed blue.
- B Acids turn blue litmus paper red, and this paper stayed blue.
Blue litmus paper dipped in grapefruit juice turns red. Is grapefruit juice an acid?
- A yes
- B no
Answer
Key: A — yes
In grapefruit juice the paper turned red.
So grapefruit juice is an acid.
Feedback per option
- A Acids turn blue litmus paper red, and this paper turned red.
- B The paper turned red, and turning blue litmus paper red is the mark of an acid.
Sour cream tastes sour. Is sour cream an acid?
- A yes
- B no
Answer
Key: A — yes
Sour cream tastes sour.
So sour cream is an acid.
Feedback per option
- A Acids taste sour, and sour cream tastes sour.
- B A sour taste is one of the properties acids share.
Blue litmus paper dipped in soy milk stays blue. Is soy milk an acid?
- A yes
- B no
Answer
Key: B — no
In soy milk the paper stayed blue.
So soy milk is not an acid.
Feedback per option
- A An acid turns blue litmus paper red; this paper stayed blue.
- B Acids turn blue litmus paper red, and this paper stayed blue.
Egg white does not taste sour, and blue litmus paper dipped in it stays blue. Is egg white an acid?
- A yes
- B no
Answer
Key: B — no
Egg white does neither.
So egg white is not an acid.
Feedback per option
- A Neither property of an acid is there: no sour taste, and the paper stayed blue.
- B Egg white shows neither property of an acid: no sour taste, and the paper stayed blue.
Pickle brine tastes sour. Is pickle brine an acid?
- A yes
- B no
Answer
Key: A — yes
Pickle brine tastes sour.
So pickle brine is an acid.
Feedback per option
- A Acids taste sour, and pickle brine tastes sour.
- B A sour taste is one of the properties acids share.
Blue litmus paper dipped in a sports drink turns red. Is the sports drink an acid?
- A yes
- B no
Answer
Key: A — yes
In the sports drink the paper turned red.
So the sports drink is an acid.
Feedback per option
- A Acids turn blue litmus paper red, and this paper turned red.
- B The paper turned red, and turning blue litmus paper red is the mark of an acid.
Talia says: "Every acid is dangerous, so vinegar must be dangerous too." Is Talia correct?
- A yes
- B no
Answer
Key: B — no
The sulfuric acid in a car battery is a strong acid that burns skin.
Not every acid is dangerous, so Talia is not correct.
Feedback per option
- A Vinegar is an acid in food; the acid that burns skin is a strong acid like the sulfuric acid in a car battery.
- B Vinegar and lemon juice are acids in food; only some acids, like the sulfuric acid in a car battery, burn skin.
Ronan says: "Cranberry juice is an acid, because it turns blue litmus paper red." Is Ronan correct?
- A yes
- B no
Answer
Key: A — yes
Cranberry juice turned the paper red.
So cranberry juice is an acid, and Ronan is correct.
Feedback per option
- A Turning blue litmus paper red is one of the properties acids share, so the paper's red end shows an acid.
- B Acids turn blue litmus paper red, so a paper that turned red shows an acid.
Sour-tasting liquids that turn blue litmus paper red all belong to one family. What is the family called?
Typed answer
Answer
Accepted: acid · acids · an acid · the acids · the acid family
So the family is the acids.
Litmus paper turns red in one family of liquids and blue in the other, so it shows which family a liquid belongs to. What kind of substance is litmus paper called?
Typed answer
Answer
Accepted: indicator · an indicator · indicators
A substance that does this is called an indicator.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Bases: the slippery family
MAT-078 · Base — Identify a substance as a base from its observable properties or indicator results.
Script
| Say | Screen |
|---|---|
| Soapy water feels slippery between your fingers, and so does washing soda solution. | [two beakers: soapy water, washing soda solution; a hand rubs fingers] |
| Red litmus paper dipped into each one turns blue. | [dark gray strips dip; the dipped ends turn hatched; legend: hatched = blue litmus paper, dark gray = red] |
| Acids turn blue litmus paper red, and these liquids do the opposite. | [a blue strip turning red beside a red strip turning blue] |
| Soapy water is slippery and bitter, and the dipped end turns blue. | [soapy water beaker; strip's dipped end turns hatched; labels: slippery, bitter] |
| Washing soda solution is slippery, and the dipped end turns blue. | [washing soda solution; same change] |
| Vinegar is sour, not slippery, and the paper stays red. | [vinegar; strip stays dark gray] |
| Ammonia cleaner is slippery, and the dipped end turns blue. | [ammonia cleaner; turns hatched] |
| Pure water has no taste, is not slippery, and the paper stays red. | [pure water; stays dark gray] |
| The three slippery liquids turned red litmus paper blue; vinegar and pure water left it red. | [five beakers; question: Does red litmus turn blue? ticks under three, crosses under two] |
| A substance that feels slippery, tastes bitter and turns red litmus paper blue is called a base. | [chip: BASE over the three ticked beakers] |
| Acids and bases are opposite families: an acid turns blue litmus paper red, and a base turns red litmus paper blue. | [the acid-and-base table: taste, feel, blue litmus, red litmus] |
| The sodium hydroxide in drain cleaner is a strong base. It burns skin. | [a drain cleaner bottle with a warning label] |
| So in a lab no liquid is touched or tasted; the test is litmus paper. | [a strip; crossed-out finger and tongue] |
| So, here's what we've seen. Bases feel slippery. | [the rule slide: the three ticked beakers; chip BASE; nothing else printed] |
| Bases taste bitter. | [label: bitter, by the soapy water] |
| Bases turn red litmus paper blue. | [the three blue strip ends] |
| Okay, now your turn. | [closing screen: bullets — • Bases feel slippery • Bases taste bitter • Bases turn red litmus paper blue] |
“Okay, now your turn.” — the attached question
Red litmus paper is dipped into soapy water. What does the dipped end do?
- A it stays red
- B it turns green
- C it turns blue
Answer
Key: C — it turns blue
Bases turn red litmus paper blue.
So the dipped end turns blue.
Feedback per option
- A The paper stays red in vinegar and pure water; in soapy water the dipped end turns blue.
- B Litmus paper turns red or blue, never green; in soapy water it turns blue.
- C Soapy water is a base, and bases turn red litmus paper blue.
Quiz after the video — the mastery check, 12 items
Which family of substances turns blue litmus paper red?
- A acids
- B indicators
- C slippery liquids
Answer
Key: A — acids
One property is that they turn blue litmus paper red.
So the family that turns blue litmus paper red is the acids.
Feedback per option
- A Acids taste sour and turn blue litmus paper red.
- B An indicator is the paper itself: it changes color to show a liquid's family.
- C The slippery liquids turn red litmus paper blue, the other way round.
Which of these is a physical property of dishwashing liquid?
- A Its price is low.
- B It feels slippery.
- C It stands on the shelf.
Answer
Key: B — It feels slippery.
You can feel that the liquid is slippery.
So its slippery feel is a physical property.
Feedback per option
- A A price is not something you can observe or measure about the liquid itself.
- B A physical property is something you can observe about a material, and its slippery feel is one.
- C Where the bottle stands is not something you can observe or measure about the liquid.
Red litmus paper dipped in tomato juice stays red. Is tomato juice a base?
- A yes
- B no
Answer
Key: B — no
In tomato juice the paper stayed red.
So tomato juice is not a base.
Feedback per option
- A A base turns red litmus paper blue; this paper stayed red.
- B Bases turn red litmus paper blue, and this paper stayed red.
Red litmus paper dipped in oven cleaner turns blue. Is oven cleaner a base?
- A yes
- B no
Answer
Key: A — yes
In oven cleaner the paper turned blue.
So oven cleaner is a base.
Feedback per option
- A Bases turn red litmus paper blue, and this paper turned blue.
- B The paper turned blue, and turning red litmus paper blue is the mark of a base.
Red litmus paper dipped in milk of magnesia turns blue. Is milk of magnesia a base?
- A yes
- B no
Answer
Key: A — yes
In milk of magnesia the paper turned blue.
So milk of magnesia is a base.
Feedback per option
- A Bases turn red litmus paper blue, and this paper turned blue.
- B The paper turned blue, and turning red litmus paper blue is the mark of a base.
Red litmus paper dipped in distilled water stays red. Is distilled water a base?
- A yes
- B no
Answer
Key: B — no
In distilled water the paper stayed red.
So distilled water is not a base.
Feedback per option
- A A base turns red litmus paper blue; this paper stayed red.
- B Bases turn red litmus paper blue, and this paper stayed red.
Buttermilk tastes sour, and red litmus paper dipped in it stays red. Is buttermilk a base?
- A yes
- B no
Answer
Key: B — no
Buttermilk tastes sour, and the paper stayed red.
So buttermilk is not a base.
Feedback per option
- A A sour taste and a paper that stays red are an acid's marks, not a base's.
- B Buttermilk shows an acid's marks: a sour taste, and red litmus paper that stays red.
Borax stirred into water makes a solution that feels slippery between the fingers. Is the borax solution a base?
- A yes
- B no
Answer
Key: A — yes
The borax solution feels slippery.
So the borax solution is a base.
Feedback per option
- A Bases feel slippery, and the borax solution feels slippery.
- B A slippery feel is one of the properties bases share.
Wood ash is stirred into water. Red litmus paper dipped in the water turns blue. Is the wood-ash water a base?
- A yes
- B no
Answer
Key: A — yes
In the wood-ash water the paper turned blue.
So the wood-ash water is a base.
Feedback per option
- A Bases turn red litmus paper blue, and this paper turned blue.
- B The paper turned blue, and turning red litmus paper blue is the mark of a base.
Kenzo says: "Vinegar is not a base, because red litmus paper stays red in it." Is Kenzo correct?
- A yes
- B no
Answer
Key: A — yes
In vinegar the paper stays red.
So vinegar is not a base, and Kenzo is correct.
Feedback per option
- A Bases turn red litmus paper blue, and vinegar leaves the paper red, so vinegar is not a base.
- B A base turns red litmus paper blue; vinegar leaves the paper red, so vinegar is not a base but an acid.
Sadie says: "A base is just a weak kind of acid." Is Sadie correct?
- A yes
- B no
Answer
Key: B — no
A base does the opposite: it turns red litmus paper blue.
A base is the opposite family, not a kind of acid, so Sadie is not correct.
Feedback per option
- A A base is the opposite family: it turns red litmus paper blue, the reverse of what an acid does.
- B Acids and bases are opposite families: an acid turns blue litmus paper red, and a base turns red litmus paper blue.
Liquids that feel slippery and turn red litmus paper blue all belong to one family. What is the family called?
Typed answer
Answer
Accepted: base · bases · a base · the bases · the base family
So the family is the bases.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
The pH scale
MAT-079 · The pH scale — Classify a substance as acidic, neutral, or basic given its pH value, using water as the neutral reference point.
Script
| Say | Screen |
|---|---|
| Lemon juice and soda water are both acids, yet lemon juice tastes far more sour. | [two beakers; a screwed-up face over the lemon juice] |
| A meter gives a liquid a number: lemon juice reads 2, soda water 4, pure water 7. | [three meters; readouts 2, 4, 7] |
| What does the number tell you? | [question mark] |
| It says how acidic or basic the liquid is. | [the three readouts; chip: HOW ACIDIC?] |
| The meter's number, from 0 to 14, is called the pH of the liquid. | [chip: pH; a bare line from 0 to 14 appears] |
| Pure water sits in the middle at pH 7, and a liquid at pH 7 is called neutral. | [marker at 7: pure water; chip: NEUTRAL] |
| The acids sit below 7: lemon juice at 2, vinegar at 3, soda water at 4. | [markers slide onto 2, 3, 4] |
| A liquid below 7 is called acidic, and the lower the pH, the more acidic it is. | [arrow pointing left under the line: more acidic; chip: ACIDIC] |
| The bases sit above 7: baking soda solution at 8, soapy water at 10, ammonia cleaner at 11. | [markers slide onto 8, 10, 11] |
| A liquid above 7 is called basic, and the higher the pH, the more basic it is. | [arrow pointing right: more basic; chip: BASIC] |
| This line from 0 to 14 is called the pH scale. Its 0 end is the most acidic end, not no acid. | [chip: THE pH SCALE over the whole line; label at 0: most acidic] |
| The pH scale runs from 0 to 14. | [the rule slide: the scale with its markers; chips ACIDIC, NEUTRAL, BASIC; nothing else printed] |
| Pure water sits in the middle, at pH 7. | [the marker at 7 glows] |
| Okay, now your turn. | [closing screen: bullets — • The pH scale runs from 0 to 14 • Pure water: pH 7, neutral • Below 7: acidic; the lower, the more acidic • Above 7: basic; the higher, the more basic] |
“Okay, now your turn.” — the attached question
Pure water is put on the pH scale. Where does its marker sit?
- A at 0
- B at 7
- C at 14
Answer
Key: B — at 7
Pure water sits in the middle, at pH 7.
So its marker sits at 7.
Feedback per option
- A 0 is the most acidic end; pure water sits in the middle.
- B Pure water sits in the middle of the scale at pH 7, and a liquid at 7 is neutral.
- C 14 is the most basic end; pure water sits in the middle.
Quiz after the video — the mastery check, 14 items
Which family of substances tastes sour and turns blue litmus paper red?
- A bases
- B acids
- C indicators
Answer
Key: B — acids
They taste sour, and they turn blue litmus paper red.
So the family is the acids.
Feedback per option
- A Bases taste bitter and turn red litmus paper blue.
- B Acids taste sour and turn blue litmus paper red.
- C An indicator is the paper that changes color, not a family of liquids.
Which family of substances feels slippery and turns red litmus paper blue?
- A acids
- B indicators
- C bases
Answer
Key: C — bases
They feel slippery, taste bitter and turn red litmus paper blue.
So the family is the bases.
Feedback per option
- A Acids taste sour and turn blue litmus paper red.
- B An indicator is the paper that changes color, not a family of liquids.
- C Bases feel slippery, taste bitter and turn red litmus paper blue.
The scale marks a liquid's pH. The liquid reads pH 9. Is the liquid acidic, neutral or basic?
- A acidic
- B neutral
- C basic
Answer
Key: C — basic
The marker at 9 sits above 7.
Above 7 a liquid is basic, so this liquid is basic.
Feedback per option
- A An acidic liquid sits below 7, and 9 sits above 7.
- B A neutral liquid sits exactly at 7, and 9 sits above 7.
- C Above 7 a liquid is basic, and 9 sits above 7.
The scale marks a liquid's pH. The liquid reads pH 3. Is the liquid acidic, neutral or basic?
- A acidic
- B neutral
- C basic
Answer
Key: A — acidic
The marker at 3 sits below 7.
Below 7 a liquid is acidic, so this liquid is acidic.
Feedback per option
- A Below 7 a liquid is acidic, and 3 sits below 7.
- B A neutral liquid sits exactly at 7, and 3 sits below 7.
- C A basic liquid sits above 7, and 3 sits below 7.
The scale marks a liquid's pH. The liquid reads pH 7. Is the liquid acidic, neutral or basic?
- A acidic
- B neutral
- C basic
Answer
Key: B — neutral
The marker sits exactly on 7.
So this liquid is neutral.
Feedback per option
- A An acidic liquid sits below 7; this marker sits exactly on 7.
- B A liquid at exactly 7, where pure water sits, is neutral.
- C A basic liquid sits above 7; this marker sits exactly on 7.
The scale marks a liquid's pH. The liquid reads pH 6. Is the liquid acidic, neutral or basic?
- A acidic
- B neutral
- C basic
Answer
Key: A — acidic
The marker at 6 sits just below 7.
Below 7 a liquid is acidic, so this liquid is acidic, only a little.
Feedback per option
- A Below 7 a liquid is acidic, and 6 sits just below 7: acidic, only a little.
- B A neutral liquid sits exactly at 7, and 6 sits one step below it.
- C A basic liquid sits above 7, and 6 sits below 7.
The scale marks a liquid's pH. The liquid reads pH 8. Is the liquid acidic, neutral or basic?
- A acidic
- B neutral
- C basic
Answer
Key: C — basic
The marker at 8 sits just above 7.
Above 7 a liquid is basic, so this liquid is basic, only a little.
Feedback per option
- A An acidic liquid sits below 7, and 8 sits above 7.
- B A neutral liquid sits exactly at 7, and 8 sits one step above it.
- C Above 7 a liquid is basic, and 8 sits just above 7: basic, only a little.
The bar chart shows the pH of two drinks. Which drink is more acidic?
- A black coffee
- B apple juice
Answer
Key: B — apple juice
Apple juice's bar reaches 3 and black coffee's reaches 5.
3 is lower, so apple juice is more acidic.
Feedback per option
- A Black coffee's bar reaches 5, higher than apple juice's 3, so black coffee is the less acidic of the two.
- B Apple juice's bar reaches 3 and black coffee's reaches 5; the lower pH is the more acidic.
The bar chart shows the pH of two liquids. Which liquid is more basic?
- A sea water
- B washing soda solution
Answer
Key: B — washing soda solution
The washing soda solution's bar reaches 11 and sea water's reaches 8.
11 is higher, so the washing soda solution is more basic.
Feedback per option
- A Sea water's bar reaches 8, lower than the washing soda solution's 11, so sea water is the less basic of the two.
- B The washing soda solution's bar reaches 11 and sea water's reaches 8; the higher pH is the more basic.
The bar chart shows the pH of two kinds of water. Which is more acidic?
- A rainwater
- B tap water
Answer
Key: A — rainwater
Rainwater's bar reaches 6 and tap water's reaches 7.
6 is lower, so rainwater is more acidic.
Feedback per option
- A Rainwater's bar reaches 6 and tap water's reaches 7; the lower pH is the more acidic.
- B Tap water's bar reaches 7, where pure water sits: neutral, not acidic at all.
Nour says: "pH 0 means there is no acid in the liquid at all." Is Nour correct?
- A yes
- B no
Answer
Key: B — no
The lower the pH, the more acidic the liquid is.
pH 0 is the most acidic end of the scale, not no acid, so Nour is not correct.
Feedback per option
- A pH 0 is the most acidic end of the scale; the lower the pH, the more acidic the liquid.
- B The lower the pH, the more acidic the liquid is, so pH 0 is the most acidic end of the scale.
Juno says: "A liquid at pH 14 is basic, and 14 is the most basic reading on the scale, because 14 is the top of the scale." Is Juno correct?
- A yes
- B no
Answer
Key: A — yes
The higher the pH, the more basic the liquid is.
14 is the highest reading on the scale, so a liquid at pH 14 has the most basic reading on the scale, and Juno is correct.
Feedback per option
- A The higher the pH, the more basic the liquid is, and 14 is the highest reading the scale has.
- B Above 7 a liquid is basic, and the higher the pH, the more basic it is; 14 is the top of the scale, so it is the most basic end.
Every liquid can be given a number from 0 to 14 that says how acidic or how basic it is. What is this number called?
Typed answer
Answer
Accepted: pH · the pH · ph · the ph · pH value · the pH value · a pH
This number is called the pH of the liquid.
Pure water reads 7, so it is neither acidic nor basic. What word names a liquid at 7?
Typed answer
Answer
Accepted: neutral · a neutral liquid · it is neutral
It is not an acid and not a base.
A liquid at 7 is called neutral.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Sort with litmus or with pH
MAT-082 · Classify a substance using an indicator or pH reading — Classify a substance as acid, base, or neutral using either a litmus result or a pH value.
Script
| Say | Screen |
|---|---|
| Suppose you have six unlabeled liquids and one clue for each. | [six beakers, P to U, a clue under each] |
| Three come with a litmus result, three with a pH reading: sort all six into acid, base or neutral. | [three empty boxes: acid, base, neutral] |
| If the clue is litmus, read the color change. Blue turning red means acid, red turning blue means base, neither changing means neutral. | [the table's first three rows appear one by one] |
| If the clue is a pH, read the scale: below 7 acid, exactly 7 neutral, above 7 base. | [the table's last three rows appear] |
| Now let's sort: liquid P turned blue litmus paper red, so P is an acid. | [P slides into the acid box] |
| Liquid Q reads pH 9, above 7, so Q is a base. | [Q slides into the base box] |
| Liquid R changed neither paper and liquid S reads pH 7, so both are neutral. | [R and S slide into the neutral box] |
| Liquid T turned red litmus paper blue, so T is a base. Liquid U reads pH 3, so U is an acid. | [T into base; U into acid] |
| So, a litmus color or a pH puts a liquid in one of three boxes: acid, base or neutral. | [the rule slide: the two-clue table and the three filled boxes; nothing else printed] |
| So P and U are acids, Q and T are bases, and R and S are neutral. | [the three filled boxes] |
| Okay, now your turn. | [closing screen: one line — "A litmus color or a pH puts a liquid in one of three boxes: acid, base or neutral."] |
“Okay, now your turn.” — the attached question
A liquid reads pH 3. Which box does it go in?
- A acid
- B base
- C neutral
Answer
Key: A — acid
3 is below 7, and a pH below 7 means acid.
So the liquid goes in the acid box.
Feedback per option
- A A pH below 7 means acid, and 3 is below 7.
- B A pH above 7 would mean base; 3 is below 7.
- C A pH of exactly 7 would mean neutral; 3 is below 7.
Quiz after the video — the mastery check, 13 items
Which litmus paper does an acid change, and to which color?
- A blue litmus paper, to red
- B red litmus paper, to blue
- C neither paper changes
Answer
Key: A — blue litmus paper, to red
One is that they turn blue litmus paper red.
So an acid changes blue litmus paper, to red.
Feedback per option
- A Acids turn blue litmus paper red.
- B Red litmus paper turning blue is a base's mark.
- C A liquid that changes neither paper is neutral.
Which litmus paper does a base change, and to which color?
- A blue litmus paper, to red
- B red litmus paper, to blue
- C neither paper changes
Answer
Key: B — red litmus paper, to blue
One is that they turn red litmus paper blue.
So a base changes red litmus paper, to blue.
Feedback per option
- A Blue litmus paper turning red is an acid's mark.
- B Bases turn red litmus paper blue.
- C A liquid that changes neither paper is neutral.
Where does a neutral liquid sit on the pH scale?
- A below 7
- B at 7
- C above 7
Answer
Key: B — at 7
A liquid at 7 is neutral.
So a neutral liquid sits at 7.
Feedback per option
- A Below 7 a liquid is acidic.
- B Pure water sits at 7, and a liquid at 7 is neutral.
- C Above 7 a liquid is basic.
The table of clues is supplied. Blue litmus paper dipped in pineapple juice turns red. Which box does pineapple juice go in?
- A acid
- B base
- C neutral
Answer
Key: A — acid
Blue litmus paper turning red means acid.
So pineapple juice goes in the acid box.
Feedback per option
- A Blue litmus paper turning red means acid.
- B Red litmus paper turning blue would mean base; here blue paper turned red.
- C Neither paper changing would mean neutral; here the paper changed.
The table of clues is supplied. A pH meter dipped in window cleaner reads 11. Which box does the window cleaner go in?
- A acid
- B base
- C neutral
Answer
Key: B — base
11 is above 7, and a pH above 7 means base.
So the window cleaner goes in the base box.
Feedback per option
- A A pH below 7 would mean acid; 11 is above 7.
- B A pH above 7 means base, and 11 is above 7.
- C A pH of exactly 7 would mean neutral; 11 is above 7.
Neither blue nor red litmus paper changes color in tap water. Which box does the tap water go in?
- A acid
- B base
- C neutral
Answer
Key: C — neutral
Neither paper changing color means neutral.
So the tap water goes in the neutral box.
Feedback per option
- A An acid would turn blue litmus paper red; nothing changed.
- B A base would turn red litmus paper blue; nothing changed.
- C Neither paper changing color means neutral.
The scale marks a liquid's pH. A pH meter dipped in a yogurt drink reads 4. Which box does the yogurt drink go in?
- A acid
- B base
- C neutral
Answer
Key: A — acid
4 is below 7, and a pH below 7 means acid.
So the yogurt drink goes in the acid box.
Feedback per option
- A A pH below 7 means acid, and 4 is below 7.
- B A pH above 7 would mean base; 4 is below 7.
- C A pH of exactly 7 would mean neutral; 4 is below 7.
Red litmus paper dipped in a laundry detergent solution turns blue. Which box does the solution go in?
- A acid
- B base
- C neutral
Answer
Key: B — base
Red litmus paper turning blue means base.
So the laundry detergent solution goes in the base box.
Feedback per option
- A Blue litmus paper turning red would mean acid; here red paper turned blue.
- B Red litmus paper turning blue means base.
- C Neither paper changing would mean neutral; here the paper changed.
The scale marks a liquid's pH. A pH meter dipped in sea water reads 8. Which box does the sea water go in?
- A acid
- B base
- C neutral
Answer
Key: B — base
8 is above 7, and a pH above 7 means base.
So the sea water goes in the base box.
Feedback per option
- A A pH below 7 would mean acid; 8 is above 7.
- B A pH above 7 means base, and 8 is above 7.
- C A pH of exactly 7 would mean neutral; 8 is one step above 7.
The scale marks a liquid's pH. A pH meter dipped in black tea reads 5. Which box does the black tea go in?
- A acid
- B base
- C neutral
Answer
Key: A — acid
5 is below 7, and a pH below 7 means acid.
So the black tea goes in the acid box.
Feedback per option
- A A pH below 7 means acid, and 5 is below 7.
- B A pH above 7 would mean base; 5 is below 7.
- C A pH of exactly 7 would mean neutral; 5 is below 7.
The scale marks a liquid's pH. A pH meter dipped in a glass of milk reads 7. Which box does the milk go in?
- A acid
- B base
- C neutral
Answer
Key: C — neutral
The reading is exactly 7, and a pH of exactly 7 means neutral.
So the milk goes in the neutral box.
Feedback per option
- A A pH below 7 would mean acid; the meter reads exactly 7.
- B A pH above 7 would mean base; the meter reads exactly 7.
- C A pH of exactly 7 means neutral.
The scale marks a liquid's pH. Blue litmus paper dipped in cola turns red, and a pH meter dipped in it reads 3. Which box does the cola go in?
- A acid
- B base
- C neutral
Answer
Key: A — acid
A pH of 3 is below 7, and a pH below 7 means acid.
Both clues put the cola in the acid box.
Feedback per option
- A Both clues agree: blue litmus turning red means acid, and a pH below 7 means acid.
- B Blue paper turning red means acid, not base; and 3 is below 7, not above.
- C The paper changed, so the cola is not neutral; and 3 is not 7.
The scale marks a liquid's pH. Red litmus paper dipped in a borax solution turns blue, and a pH meter dipped in it reads 9. Which box does the borax solution go in?
- A acid
- B base
- C neutral
Answer
Key: B — base
A pH of 9 is above 7, and a pH above 7 means base.
Both clues put the borax solution in the base box.
Feedback per option
- A Red paper turning blue means base, not acid; and 9 is above 7, not below.
- B Both clues agree: red litmus turning blue means base, and a pH above 7 means base.
- C The paper changed, so the borax solution is not neutral; and 9 is not 7.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Add a base to an acid: the pH climbs
MAT-081 · Neutralisation — Predict how the pH of an acidic solution changes when a base is added to it.
Script
| Say | Screen |
|---|---|
| Suppose stomach acid at pH 2 gives you heartburn. You take two antacid tablets. | [a cartoon stomach; the pH scale with a marker at 2: stomach acid; two tablets] |
| The tablets are a base, and the burning stops. What did the base do to the pH? | [question mark over the marker] |
| It made the pH climb. | [the marker nudges up from 2] |
| Stomach acid is dilute hydrochloric acid, and the tablet's magnesium hydroxide is a base. | [two labels: hydrochloric acid; magnesium hydroxide] |
| Magnesium hydroxide and hydrochloric acid react to make magnesium chloride and water. | [strip: magnesium hydroxide + hydrochloric acid → magnesium chloride + water] |
| The reaction uses up some of the acid, so the liquid is less acidic. | [in the beaker, marked acid particles wink out one by one as tablet pieces dissolve; the liquid level stays where it is] |
| A less acidic liquid has a higher pH, so watch the marker climb toward 7. | [the marker slides from 2 toward 7 as base is poured in] |
| Exactly enough base uses up every bit of acid: the marker reaches 7, and the liquid is neutral. | [marker stops on 7; chip: NEUTRAL] |
| More base than that is left over with nothing to react with: the marker climbs past 7. | [more base pours in; marker slides on to 9; label: too much base] |
| An acid and a base reacting and using each other up is called neutralization. | [chip: NEUTRALIZATION over the strip] |
| Lab hydrochloric acid is a strong acid that burns skin, so goggles and gloves are worn. | [a bottle with a warning label; goggles and gloves] |
| So, when a base is added to an acid, the base uses up some of the acid, and the pH climbs toward 7. | [the rule slide: the scale with the marker risen from 2 toward 7; chip NEUTRALIZATION; nothing else printed] |
| So the tablets used up some of the stomach acid, its pH climbed, and the burning stopped. | [the stomach; the marker up from 2] |
| Okay, now your turn. | [closing screen: one line — "When a base is added to an acid, the base uses up some of the acid, and the pH climbs toward 7."] |
“Okay, now your turn.” — the attached question
A base is poured into an acid at pH 2. Which way does the pH marker move?
- A toward 0
- B it does not move
- C toward 7
Answer
Key: C — toward 7
Less acid means a less acidic liquid, with a higher pH.
So the marker moves toward 7.
Feedback per option
- A Toward 0 would mean more acid; the base uses acid up.
- B The base reacts with the acid and uses some of it up, so the marker moves.
- C The base uses up some of the acid, so the liquid is less acidic and the marker climbs toward 7.
Quiz after the video — the mastery check, 13 items
A liquid reads pH 4. Is the liquid neutral, acidic or basic?
- A neutral
- B acidic
- C basic
Answer
Key: B — acidic
4 sits below 7.
Below pH 7 a liquid is acidic, so this liquid is acidic.
Feedback per option
- A A neutral liquid sits exactly at 7, and 4 sits below 7.
- B Below pH 7 a liquid is acidic, and 4 sits below 7.
- C A basic liquid sits above 7, and 4 sits below 7.
In a chemical reaction, what forms?
- A the same substances, warmer
- B the same substances in a new state
- C new substances
Answer
Key: C — new substances
They join new partners.
So new substances form.
Feedback per option
- A Warming a substance changes its temperature, not its atoms' partners.
- B A new state of the same substance is a change of state, not a chemical reaction.
- C In a chemical reaction the atoms let go of their old partners and join new ones, so new substances form.
A beaker of dilute nitric acid reads pH 2. A student stirs in some potassium hydroxide solution, a base. What happens to the pH?
- A it falls
- B it stays at 2
- C it rises
Answer
Key: C — it rises
Less acid means the liquid is less acidic.
A less acidic liquid has a higher pH, so the pH rises toward 7.
Feedback per option
- A The base uses up some of the acid, and less acid means a higher pH, not a lower one.
- B The base reacts with the acid and uses some of it up, so the pH does not stay put.
- C The base uses up some of the acid; less acid means the liquid is less acidic, so the pH rises toward 7.
A beaker of dilute sulfuric acid reads pH 1. A student adds sodium hydroxide solution, a base, a little at a time, and the reading climbs to 5. Explain why the pH climbed.
Starter: The base reacts with…
Answer
Model answer · ['the base reacts with the acid and uses up some of it', 'less acid means the liquid is less acidic', 'a less acidic liquid has a higher pH, so the pH climbed toward 7'] points
The reaction uses up some of the acid.
Less acid means the liquid is less acidic.
A less acidic liquid has a higher pH.
So the pH climbed from 1 to 5.
The marker shows a liquid at pH 4, and a base is added. Which way does the pH move?
- A down, toward 0
- B up, toward 7
- C it does not move
Answer
Key: B — up, toward 7
Less acid means the liquid is less acidic.
So the pH moves up, toward 7.
Feedback per option
- A A lower pH would mean more acid; the base uses acid up, so the pH climbs.
- B The base uses up some of the acid, so the liquid is less acidic and the pH climbs toward 7.
- C The base reacts with the acid and uses some of it up, so the pH moves.
The marker shows a liquid at pH 12, and an acid is added. Which way does the pH move?
- A up, toward 14
- B down, toward 7
- C it does not move
Answer
Key: B — down, toward 7
Less base means the liquid is less basic.
So the pH moves down, toward 7.
Feedback per option
- A A higher pH would mean more base; the acid uses base up, so the pH falls.
- B The acid uses up some of the base, so the liquid is less basic and the pH falls toward 7.
- C The acid reacts with the base and uses some of it up, so the pH moves.
The liquid starts at pH 2, and a little base is added, not enough to use up all the acid. Where is the pH now?
- A still below 7
- B exactly 7
- C above 7
Answer
Key: A — still below 7
Acid is left, so the liquid is still acidic.
So the pH has climbed but is still below 7.
Feedback per option
- A Some acid is used up but some is left, so the liquid is still acidic and the pH is still below 7.
- B The pH reaches 7 only when exactly enough base has used up all the acid.
- C The pH passes 7 only when more base than needed has gone in.
The liquid starts at pH 2, and exactly enough base is added to use up all the acid. Where is the pH now?
- A still below 7
- B exactly 7
- C above 7
Answer
Key: B — exactly 7
No acid and no base is left over.
So the liquid is neutral, at exactly 7.
Feedback per option
- A A pH below 7 would mean acid is left; here every bit of acid is used up.
- B Every bit of acid is used up and no base is left over, so the liquid is neutral at pH 7.
- C A pH above 7 would mean base is left over; here exactly enough went in.
The liquid starts at pH 2, and more base than needed is added. Where is the pH now?
- A still below 7
- B exactly 7
- C above 7
Answer
Key: C — above 7
Base is left over with no acid to react with.
So the liquid is basic, and the pH is above 7.
Feedback per option
- A A pH below 7 would mean acid is left; here all the acid is used up and base is left over.
- B A pH of exactly 7 needs exactly enough base; here more than that went in.
- C All the acid is used up and base is left over, so the liquid is basic and the pH is above 7.
Gideon says: "Adding an acid to a base makes the base's pH fall." Is Gideon correct?
- A yes
- B no
Answer
Key: A — yes
Less base means the liquid is less basic.
A less basic liquid has a lower pH, so the pH falls, and Gideon is correct.
Feedback per option
- A The acid uses up some of the base, so the liquid is less basic and its pH falls toward 7.
- B The acid reacts with the base and uses some of it up; less base means a lower pH.
Odette says: "Any amount of base makes an acid neutral at once." Is Odette correct?
- A yes
- B no
Answer
Key: B — no
Acid is left, so the liquid is still acidic.
The pH reaches 7 only with exactly enough base, so Odette is not correct.
Feedback per option
- A A little base uses up only a little acid; the pH climbs step by step and reaches 7 only with exactly enough base.
- B A little base uses up a little acid, so the pH climbs step by step; only exactly enough base brings it to 7.
Acid rain has made a lake's water acidic, at pH 5. Workers spread powdered slaked lime, a base, into the lake. What happens to the lake's pH?
- A it rises toward 7
- B it stays at 5
- C it falls toward 0
Answer
Key: A — it rises toward 7
It reacts with the acid in the lake water and uses some of it up.
Less acid means the water is less acidic, so its pH rises toward 7.
Feedback per option
- A The slaked lime, a base, uses up some of the acid in the water, so the water is less acidic and its pH rises toward 7.
- B The slaked lime reacts with the acid in the water and uses some of it up, so the pH does not stay put.
- C Falling would mean more acid; the base uses acid up.
A base is added to an acid; the two react and use each other up, and the pH moves toward 7. What is this reaction called?
Typed answer
Answer
Accepted: neutralization · neutralisation · a neutralization · a neutralisation · neutralizing · neutralising
An acid and a base reacting and using each other up is called neutralization.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Where the salt comes from
MAT-080 · Salt as the product of neutralisation — Explain where the salt formed in an acid–base reaction comes from.
Script
| Say | Screen |
|---|---|
| Suppose you add sodium hydroxide, a base, to hydrochloric acid, just enough, and the mixture reads pH 7. | [two beakers pour into one; a meter reads pH 7] |
| When the water is boiled away, white crystals are left: sodium chloride, table salt. | [a dish; grains appear on its floor; label: sodium chloride] |
| Neither liquid had any salt in it, so where did the salt come from? | [question mark over the crystals] |
| It came from both the acid and the base. | [the two beakers; arrows to the crystals] |
| The atoms in a new substance come from the substances that were there before. | [chip: SAME ATOMS] |
| This neutralization makes sodium chloride and water. | [strip: hydrochloric acid + sodium hydroxide → sodium chloride + water] |
| The acid has two parts: a hydrogen part and a chloride part. | [two joined blocks: hydrogen part | chloride part] |
| The base has two parts: a sodium part and a hydroxide part. | [two joined blocks: sodium part | hydroxide part] |
| Watch the parts swap partners. | [the blocks separate and slide] |
| The sodium part from the base joins the chloride part from the acid: sodium chloride. | [sodium part | chloride part; label: sodium chloride] |
| The leftover parts, hydrogen from the acid and hydroxide from the base, join: water. | [hydrogen part | hydroxide part; label: water] |
| A substance made this way is called a salt. | [chip: SALT; a row: sodium chloride, magnesium chloride, potassium sulfate] |
| So, here's what we've seen. A neutralization makes a salt and water. | [the rule slide: the four blocks after the swap; chip SALT; nothing else printed] |
| The base gives the salt its metal part. | [the sodium part colored in from the base] |
| The acid gives the salt its other part. | [the chloride part colored in from the acid] |
| So the crystals' sodium came from the base and their chloride from the acid, and no atom appeared or vanished. | [the crystals; the two parts colored in from their reactants] |
| Okay, now your turn. | [closing screen: bullets — • A neutralization makes a salt and water • The base gives the salt its metal part • The acid gives the salt its other part] |
“Okay, now your turn.” — the attached question
Sodium hydroxide neutralizes hydrochloric acid, and the parts swap partners. Which part does the sodium part join?
- A the hydrogen part
- B the chloride part
- C the hydroxide part
Answer
Key: B — the chloride part
The sodium part from the base joins the chloride part from the acid.
Sodium joined to chloride is sodium chloride, the salt.
Feedback per option
- A The hydrogen part joins the hydroxide part to make water.
- B The sodium part from the base joins the chloride part from the acid: sodium chloride, the salt.
- C The hydroxide part is the sodium part's old partner; it joins the hydrogen part to make water.
Quiz after the video — the mastery check, 11 items
A base is added to an acid, and the two use each other up. What is this reaction called?
- A neutralization
- B dissolving
- C conservation of mass
Answer
Key: A — neutralization
The two use each other up.
An acid and a base reacting and using each other up is called neutralization.
Feedback per option
- A An acid and a base reacting and using each other up is called neutralization.
- B Dissolving spreads a substance through a liquid without a reaction.
- C Conservation of mass is a law about the total mass in a reaction, not the name of a reaction.
Where do the atoms in a new substance come from?
- A from the heat that was added during the change
- B from the substances that were there before
- C the change makes them out of nothing
Answer
Key: B — from the substances that were there before
No atom vanishes.
So the atoms in a new substance come from the substances that were there before.
Feedback per option
- A Heat is not made of atoms.
- B The atoms in a new substance come from the substances that were there before.
- C No atom is made from nothing.
Sodium chloride is made of two kinds of atom joined together in a fixed pattern. What kind of substance is it?
- A an element
- B a mixture
- C a compound
Answer
Key: C — a compound
The atoms are joined together in a fixed pattern.
So sodium chloride is a compound.
Feedback per option
- A An element is made of only one kind of atom.
- B In a mixture the substances are mingled, not joined in a fixed pattern.
- C A substance made of two or more kinds of atom joined together in a fixed pattern is called a compound.
Sulfuric acid and potassium hydroxide, a base, react in just the right amounts. Which products form?
- A water only
- B a salt and water
- C a salt and a gas
Answer
Key: B — a salt and water
The leftover parts, hydrogen and hydroxide, join to make water.
So the two products are a salt and water.
Feedback per option
- A Water is one product; the metal part and the acid's other part make the second, a salt.
- B The base's metal part joins the acid's other part as a salt, and the leftover parts make water.
- C No gas forms; the leftover parts, hydrogen and hydroxide, make water.
Nitric acid and calcium hydroxide, a base, react in just the right amounts. The products are calcium nitrate, a salt, and water. Explain where the two parts of the calcium nitrate came from.
Starter: The base gives…
Answer
Model answer · ['the base gives the salt its metal part, so the calcium part came from the calcium hydroxide', 'the acid gives the salt its other part, so the nitrate part came from the nitric acid'] points
So the calcium part came from the calcium hydroxide.
The acid gives the salt its other part.
So the nitrate part came from the nitric acid.
A student writes the word equation nitric acid + potassium hydroxide → potassium nitrate + water. Which product is the salt?
- A potassium nitrate
- B water
Answer
Key: A — potassium nitrate
Potassium from the base joined nitrate from the acid.
So potassium nitrate is the salt.
Feedback per option
- A Potassium nitrate is the base's metal part, potassium, joined to the acid's other part, nitrate: a salt.
- B Water is made from the leftover parts, hydrogen and hydroxide; the salt is the other product.
Hattie says: "The salt was already dissolved in the acid; the base just made it show up." Is Hattie correct?
- A yes
- B no
Answer
Key: B — no
Before the base was added, no metal part was in the acid.
So the salt was not there already, and Hattie is not correct.
Feedback per option
- A The salt's metal part came from the base, so the salt could not have been in the acid before the base arrived.
- B The salt is made in the reaction: its metal part comes from the base and its other part from the acid.
Ishaan says: "Every atom in the salt was in the acid or the base before the reaction." Is Ishaan correct?
- A yes
- B no
Answer
Key: A — yes
The salt's metal part was in the base, and its other part was in the acid.
So every atom in the salt was there before the reaction, and Ishaan is correct.
Feedback per option
- A The atoms in a new substance come from the substances that were there before, and the salt's atoms were in the acid and the base.
- B No atom appeared in the reaction: the salt's metal part was in the base and its other part was in the acid.
In a neutralization, the salt calcium sulfate forms. Which reactant gave the salt its calcium part?
- A the base
- B the acid
Answer
Key: A — the base
Calcium is the metal part of calcium sulfate.
So the base gave the calcium part.
Feedback per option
- A The base gives the salt its metal part, and calcium is the metal part.
- B The acid gives the salt its other part, here the sulfate part.
A student writes the word equation nitric acid + magnesium hydroxide → magnesium nitrate + water. Which reactant gave the nitrate part of the salt?
- A the base
- B the acid
Answer
Key: B — the acid
Nitrate is nitric acid's other part.
So the acid gave the nitrate part of magnesium nitrate.
Feedback per option
- A The base gives the salt its metal part, magnesium; the nitrate part came from the acid.
- B The acid gives the salt its other part, and nitrate is the acid's other part.
Potassium sulfate, calcium nitrate and magnesium sulfate are all made when a base's metal part joins an acid's other part. In chemistry, what is this family of substances called?
Typed answer
Answer
Accepted: salt · salts · a salt · the salts · the salt family
A substance made this way is called a salt.
In chemistry, salt names the whole family.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Summary: Acids and bases
Script, part 1 (132 words)
| Say | Screen |
|---|---|
| Here is everything we found out about acids and bases. | [a still: the three acid beakers and the soapy water, with their strips] |
| Acids taste sour. Acids turn blue litmus paper red. | [three beakers; blue strips with red ends; chip: ACID] |
| Bases feel slippery. Bases taste bitter. Bases turn red litmus paper blue. | [soapy water; a red strip with a blue end; chip: BASE] |
| Litmus paper changes color to show which family a liquid belongs to. A substance that does this is called an indicator. | [a strip; chip: INDICATOR] |
| The pH scale runs from 0 to 14. Pure water sits in the middle, at pH 7. A liquid at pH 7 is called neutral. | [the scale; marker at 7; chip: NEUTRAL] |
| Below pH 7 a liquid is acidic. The lower the pH, the more acidic it is. | [markers at 2, 3, 4; arrow left; chip: ACIDIC] |
| Above pH 7 a liquid is basic. The higher the pH, the more basic it is. | [markers at 8, 10, 11; arrow right; chip: BASIC] |
| And a litmus color or a pH puts a liquid in one of three boxes: acid, base or neutral. | [the two-clue table; the three boxes] |
| Okay, now your turn. | [closing screen: bullets — • Acids: sour; blue litmus paper turns red • Bases: slippery, bitter; red litmus paper turns blue • pH scale 0 to 14; pure water pH 7, neutral • Below 7 acidic, above 7 basic] |
“Okay, now your turn.” — the check question between the parts
A liquid turns blue litmus paper red. Which family is it in?
- A It is a base.
- B It is an acid.
Answer
Key: B — It is an acid.
This liquid turned blue litmus paper red.
So it is an acid.
Feedback per option
- A A base turns red litmus paper blue; this liquid turned blue litmus paper red.
- B Acids turn blue litmus paper red.
Script, part 2 (112 words)
| Say | Screen |
|---|---|
| Here is everything we found out about what happens when an acid and a base react. | [a still: the scale with a marker at 7; the strip magnesium hydroxide + hydrochloric acid → magnesium chloride + water] |
| When a base is added to an acid, the base uses up some of the acid. Less acid means the liquid is less acidic. | [the marker at 2 and a second marker nearer 7] |
| A less acidic liquid has a higher pH. So the pH climbs toward 7. | [arrow from 2 toward 7] |
| Exactly enough base takes the pH to 7. More base than that pushes the pH past 7. | [markers at 7 and at 9] |
| An acid and a base reacting and using each other up is called neutralization. | [the strip; chip: NEUTRALIZATION] |
| A neutralization makes a salt and water. The base gives the salt its metal part. The acid gives the salt its other part. | [the four blocks after the swap; label: sodium chloride, the salt; chip: SALT] |
| Okay, now your turn. | [closing screen: bullets — • A base added to an acid uses up acid, so the pH climbs toward 7 • Exactly enough base: pH 7; more: past 7 • Acid + base using each other up: neutralization • A neutralization makes a salt and water] |
“Okay, now your turn.” — the two questions after part 2
In a neutralization, which reactant gives the salt its metal part?
- A the base
- B the acid
- C the water
Answer
Key: A — the base
The base's metal part joins the acid's other part to make the salt.
So the base gives the salt its metal part.
Feedback per option
- A The base gives the salt its metal part, and the acid gives the salt its other part.
- B The acid gives the salt its other part, not the metal part.
- C Water is a product of the reaction, not a reactant.
Exactly enough base is added to an acid to use up every bit of it. What is the pH at the end?
- A below 7
- B exactly 7
- C above 7
Answer
Key: B — exactly 7
The liquid is then neutral.
A neutral liquid has pH 7.
Feedback per option
- A Below 7 would mean some acid is left; exactly enough base leaves none.
- B With every bit of acid used up, the liquid is neutral, and a neutral liquid has pH 7.
- C Above 7 would mean base is left over with nothing to react with; that takes more than exactly enough.
What to judge
Is this content better than the current alternative students have (PhysicsGraph / Edmentum)?
8/10 on:
- Clear and concise language
- Physics accuracy (read as chemistry accuracy here; his line as pasted for HS Physics)
- No "clangers" (content that causes a problematic misconception)
- Appropriate questions
- Initial testing
- Expansion into harder questions (no exam)
- The tasks should use similar language to that of the lesson
Gut check: better than the alternative? Would a student benefit? Full criteria
Applied without asking
Rulings you have already given; in force on every card above, not re-asked.
- Every video ends “Okay, now your turn.” with one easy, video-dependent question (the XP gate).
- An intro video is at most 120 words and teaches nothing: it opens the question the topic answers.
- A summary video is at most 300 words: everything taught, in order, just before the PP100.
- A lesson script is at most 200 words.
- Each lesson ships as both a video and an article; the article is not under review here.
The topic’s fixed wording (the lexicon the scripts repeat)
- Acids taste sour. Acids turn blue litmus paper red.
- Bases feel slippery. Bases taste bitter. Bases turn red litmus paper blue.
- Litmus paper changes color to show which family a liquid belongs to. A substance that does this is called an indicator.
- The pH scale runs from 0 to 14. Pure water sits in the middle, at pH 7. A liquid at pH 7 is called neutral.
- Below pH 7 a liquid is acidic. The lower the pH, the more acidic it is.
- Above pH 7 a liquid is basic. The higher the pH, the more basic it is.
- A litmus color or a pH puts a liquid in one of three boxes: acid, base or neutral.
- When a base is added to an acid, the base uses up some of the acid. Less acid means the liquid is less acidic. A less acidic liquid has a higher pH. So the pH climbs toward 7.
- Exactly enough base takes the pH to 7. More base than that pushes the pH past 7.
- An acid and a base reacting and using each other up is called neutralization.
- A neutralization makes a salt and water. The base gives the salt its metal part. The acid gives the salt its other part.
Scripts, questions and quizzes are read from the course content as it stands today; the student site for this topic is here.